It is useful to be able to use, depending on the situation, both visual information obtained through a specialized camera for a range that is outside of what can be obtained through the naked eye to obtain visual information that cannot be obtained by the naked eye, depending on the situation. It is also useful to use visual information through the naked eye. For example, in aircrafts, or in applications for the purposes of crime prevention, security, and defense, and so forth, there have been proposals for helmets with display systems (e.g., a head-mounted display system) wherein night-vision cameras have been mounted on helmets (see, for example, Japanese Unexamined Patent Application Publication H9-188911 and Japanese Examined Patent Application Publication 2001-515150). In this type of helmet with display system, the visual information that can be obtained through the night-vision camera can be projected onto the visor (an eye-proximate optical system) of the helmet. Therefore the wearer of the helmet with display system (e.g., the observer) is able to view clearly even in environments such as the night.
Moreover, in applications for the purposes of performing rescue operations by firefighters and rescue teams, there have been proposals for helmets with display systems (e.g., head-mounted display systems) wherein infrared cameras have been mounted on the helmets (see, for example, Japanese Unexamined Patent Application Publication H8-054282). In this type of helmet with a display system, the visual information that can be obtained through the infrared camera can be projected onto the visor (an eye-proximate optical system) of the helmet. Therefore, the wearer of the helmet with display system (the observer) is able to see more clearly even in an environment such as the scene of a disaster.
FIG. 9 is a side view diagram illustrating one example of a helmet with a display system (i.e., a head-mounted display system) that is worn on the head of a wearer, consistent with an embodiment of the present invention, where FIG. 10 is a plan view diagram illustrating schematically the structure of the helmet with display system 100 that is illustrated in FIG. 9, consistent with an embodiment of the present invention.
The helmet with display system 100 comprises: a helmet 1 that is worn on the head of a wearer P; a visor (an eye-proximate optical system) 13 that is placed in front of the wearer P; a left-eye night-vision camera 2L, placed on the left side of the helmet 1, for capturing a left-eye image, a right-eye night-vision camera 2R, placed on the right side of the helmet 1, for capturing a right-eye image; a left-eye display unit (projecting mechanism) 110L that is placed to the upper left of the wearer P, a right-eye display unit (projecting mechanism) 110R that is placed to the upper right of the wearer P; and a video signal processing unit 3 for controlling the left-eye night-vision camera 2L, the right-eye night-vision camera 2R, the left-eye display unit 110L, and the right-eye display unit 110R.
In one embodiment, helmet 1 is a semi-spherical shape that covers the head of the wearer, and wherein the face is open.
In one embodiment, visor 13 has a specific curved surface shape. Visor 13 is structured from a half mirror, a hologram element, or the like. In one embodiment, the visor 13 is supported on the helmet 1 in a state wherein it can be slid upward or downward. When the visor 13 is lowered, it is positioned in front of the left eye EL and the right eye ER of the wearer P.
The curved surface shape of the visor is, for example, a concave surface of an off-axis toric shape wherein the absolute value of the curvature 1/Rx in the X direction is large and the absolute value of the curvature 1/Ry in the Y direction is small. The “off-axis toric shape” is expressed by a surface defined by the shape function provided by Equation (1), below, in an XYZ coordinate space, wherein the surface has a center that is eccentric relative to the axis of symmetry of the surface.
                                              ⁢                  [                      EQUATION            ⁢                                                  ⁢            1                    ]                ⁢                                                                                      Z        =                                                            c                x                            ⁢                              X                2                                      +                                          c                y                            ⁢                              Y                2                                                          1            +                                          1                -                                                      (                                          1                      +                                              k                        x                                                              )                                    ⁢                                      c                    x                    2                                    ⁢                                      X                    2                                                  -                                                      (                                          1                      +                                              k                        y                                                              )                                    ⁢                                      c                    y                    2                                    ⁢                                      Y                    2                                                                                                          (        1        )            
Here, cx and cy are the curvatures 1/Rx and 1/Ry in the X and Y directions, and kx and ky are the second-order curved-surface coefficients in the X direction and the Y direction.
The left-eye night-vision camera 2L and the right-eye night-vision camera 2R have a night-vision function that amplifies the intensity of the received visible light or infrared light (with a wavelength of, for example, more than 610 nm). This makes it possible to see an observed object that emits or reflects infrared light in the surroundings, even under dark conditions (e.g., at night).
Moreover, in order to enable a stereoscopic view of the observed object, the left-eye night-vision camera 2L and the right-eye night-vision camera 2R are positioned on the left side and the right side, respectively, of helmet 1 with a specific distance between the cameras, with the individual imaging directions (optical axes) thereof in a direction that is perpendicular to the direction of separation between the cameras.
A video signal processing unit 3 inputs the video signals (visual information) from the left-eye night-vision camera 2L and the right-eye night-vision camera 2R, and controls the outputting of the image signals from the left-eye display unit 110L and the right-eye display unit 110R.
In one embodiment of the display system 100, the left-eye image displaying light that is projected from the left-eye display unit 110L is directed towards the left eye EL of the wearer P through reflecting on the reflective surface of the visor 13, and the right-eye image displaying light that is projected from the right-eye display unit 110R is directed to the right eye RE of the wearer through reflecting on the reflective surface of the visor 13. The result is that the wearer P is able to view a virtual image of the observed object stereoscopically, and able to view the actual objects that are ahead through the light that passes through the visor 13.
However, the reflective surface of the visor 13, as described above, typically has a specific curved surface shape, and the head of the wearer P is located at the front face of the visor 13, and thus the left-eye image displaying light that is emitted from the left-eye display unit 110L and the right-eye image displaying light that is emitted from the right-eye display unit 110R is projected toward the reflecting face of the visor 13 in order to avoid the head of the wearer P. Accordingly, a non-coaxial optical system is structured to form a virtual image without distortion in front of the wearer P.
FIG. 5 is a cross-sectional diagram illustrating one example of a schematic structure of a conventional left-eye display unit. FIG. 6 is a perspective diagram of the light source illustrated in FIG. 5.
The left-eye display unit 110L has a light source 114L, a transmissive flat-panel liquid crystal display 11L, and a square cylindrical plastic housing 115L. The light source 114L is placed within one end side of the square cylindrical housing 115L, and some optical elements 12L are placed on the inside of the other end portion of the cylindrical housing 115L, where the transmissive flat-panel liquid crystal display 11L is placed within the cylindrical housing 115L in the center portion thereof.
The transmissive flat-panel liquid crystal display 11L forms an image on the flat-panel (which is, for example, 1 inch) based on an image signal from the video signal processing unit 3.
However, in the helmet with display system 100 there is a non-coaxial optics system that is structured from some optical elements 12L, for the reasons described above, and thus the flat-panel liquid crystal display 11L is secured within the housing 115L so that the direction BL of the normal line of the flat-panel is inclined at an angle α relative to the pupillary axial direction AL.
The light source 114L has a substrate 121 that is made from a flat plate of plastic, and a plurality (e.g., 65) light-emitting diodes 22. A plurality of light-emitting diodes 22 are placed two-dimensionally in a checkerboard grid shape on the upper face (in an XY plane) of the substrate 121, where each light-emitting diode 22 emits light in the direction that is perpendicular to the XY plane (that is, in the Z direction). Note that in regards to the light that is emitted from each individual light-emitting diode 22, the intensity of the emitted light from the center portion in the forward direction (the direction of the optical axis of the light-emitting diode) is high, where the intensity of light-emission becomes lower, closer toward the edge.
Moreover, the light source 114L is secured within the housing 15L so that the Z direction is coincident with the pupillary axial direction AL. As a result, the image that is displayed on the flat-panel is illuminated. At this time, the Z axis is coincident with the pupillary axial direction AL, and thus bright left-eye image displaying light is directed to the left eye EL of the wearer P.
In one embodiment, the right-eye display unit 110R has the same structure as the left-eye display unit 110L.
However, in the left-eye display unit 110L as described above, even though the bright left-eye image displaying light is directed towards the left eye EL of the user, it is the left-eye image displaying light that is non-uniformity that is directed towards the left eye EL of the wearer P. Specifically, because the distance between the top end portion of the flat-panel and the light-emitting diodes 22 is far, the brightness at the top end portion of the virtual image of the observed object is low, and because the distance between the bottom end portion of the flat-panel and the light-emitting diodes 22 is near, the brightness of the bottom end portion of the virtual image of the observed object is high.
Accordingly, in one aspect the present applicant has developed a left-eye display unit wherein it is possible to reduce the brightness non-uniformity of virtual images of observed objects. FIG. 7 is a cross-sectional diagram illustrating one example of a schematic structure of a left-eye display unit. Note that for those portions that are identical to those of the left-eye display unit 110L, identical codes may be assigned.
In the left-eye display unit 130L, the direction of emission of the light that is emitted from each individual light-emitting diode 22 is coincident with the pupillary axial direction AL, and the attachment within the housing 115L is such that there are equal distances L1 between each individual light-emitting diode 22 and the transmissive flat-panel liquid crystal display 11L. This illuminates the image displayed by the flat panel. At this time, the direction of emission of light that is emitted from the individual light-emitting diodes 22 is coincident with the pupillary axial direction AL. That is, the bright left-eye image displaying light is directed to the left eye EL of the wearer P. In one embodiment, the light-emitting diodes 22 are each placed so as to each be at the identical distance L1 from the flat panel. That is, the left-eye image displaying light wherein the non-uniformity in brightness is reduced is directed toward the left eye EL of the wearer P so that the brightness at the upper edge portion of the virtual image of the observed object is equal to the intensity at the lower edge portion.
However, in the left-eye display unit 130L, when compared to the left-eye display unit 110L, even though the left-eye image displaying light, the brightness non-uniformity of the virtual image of the observed object that is reduced is directed toward the left eye EL of the wearer P. The intensity of the peripheral portion of the virtual image of the observed object is low, and there is a problem in that there is brightness non-uniformity, wherein the intensity is low in the peripheral portions of the virtual image of the observed object, and wherein the intensity is high in the central portion of the virtual image of the observed object.